单项选择题

What were the Mars' seasonal changes in color believed to be

A．The natural changes on the planet.
B．The seasonal cycles.
C．The movement of some life form.
D．The storm of dust in its atmosphere.

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单项选择题

A variety of extracurricular activities are added in American schools （）

A．to help students climb the education ladder
B．to enrich students' dull life at school
C．to help students become more successful in later life
D．to extend college education down into elementary schools

单项选择题

Which of the following can be the best title for this passage

A．Education and Success
B．Extracurricular Activities at School
C．Athletic Sports
D．Intellectual Achievement